Tumor progression inhibits the induction of multifunctionality in adoptively transferred tumor‐specific CD8+ T cells

It is becoming increasingly evident that the multifunctionality of effector cells at the single‐cell level is an important factor to predict the quality of T‐cell response in immunological protection. The significance of the multifunctionality of T cells in anti‐tumor immunity, however, remains unclear. Here, we assessed the IFN‐γ and TNF‐α production and CD107a mobilization in adoptively transferred tumor‐antigen‐specific CD8⁺ T cells at the single‐cell level. Tumor growth of the murine fibrosarcoma CMS5 was found to limit the induction of multifunctionality in the transferred cells. These cells exhibited insufficient acquisition of the CD25^highGITR^highCD62L^low phenotype and reduced infiltration in tumor. Depletion of Treg facilitated the induction of high multifunctionality of the transferred cells even in the hosts with progressing tumor, leading to enhanced tumor regression. The multifunctionality of the transferred cells correlated with in vivo CTL activity, and T cells with high multifunctionality harvested from hosts with successful therapy induced tumor regression when re‐transferred into the tumor‐bearing hosts. These data suggest that the appearance of multifunctional CD8⁺ effector T cells in vivo is a critical determinant of the success of anti‐tumor immunotherapy and Treg play an important role in the mechanism inhibiting the induction of multifunctionality in effector cells.     

Positive selection of self‐antigen‐specific CD8+ T cells by hematopoietic cells

In contrast to thymic epithelial cells, which induce the positive selection of conventional CD8⁺ T cells, hematopoietic cells (HCs) select innate CD8⁺ T cells whose Ag specificity is not fully understood. Here we show that CD8⁺ T cells expressing an H‐Y Ag‐specific Tg TCR were able to develop in mice in which only HCs expressed MHC class I, when HCs also expressed the H‐Y Ag. These HC‐selected self‐specific CD8⁺ T cells resemble innate CD8⁺ T cells in WT mice in terms of the expression of memory markers and effector functions, but are phenotypically distinct from the thymus‐independent CD8⁺ T‐cell population. The peripheral maintenance of H‐Y‐specific CD8⁺ T cells required presentation of the self‐Ag and IL‐15 on HCs. HC‐selected CD8⁺ T cells in mice lacking the Tg TCR also showed these features. Furthermore, by using MHC class I tetramers with a male Ag peptide, we found that self‐Ag‐specific CD8⁺ T cells in TCR non‐Tg mice could develop via HC‐induced positive selection, supporting results obtained from H‐Y TCR Tg mice. These findings indicate the presence of self‐specific CD8⁺ T cells that are positively selected by HCs in the peripheral T‐cell repertoire.     

Phenotypic switch of CD8+ T cells reactivated under hypoxia toward IL‐10 secreting,poorly proliferative effector cells

CD8⁺ T cells controlling pathogens or tumors must function at sites where oxygen tension is frequently low, and never as high as under atmospheric culture conditions. However, T‐cell function in vivo is generally analyzed indirectly, or is extrapolated from in vitro studies under nonphysiologic oxygen tensions. In this study, we delineate the role of physiologic and pathologic oxygen tension in vitro during reactivation and differentiation of tumor‐specific CD8⁺ T cells. Using CD8⁺ T cells from pmel‐1 mice, we observed that the generation of CTLs under 5% O₂, which corresponds to physioxia in lymph nodes, gave rise to a higher effector signature than those generated under atmospheric oxygen fractions (21% O₂). Hypoxia (1% O₂) did not modify cytotoxicity, but decreasing O₂ tensions during CTL and CD8⁺ tumor‐infiltrating lymphocyte reactivation dose‐dependently decreased proliferation, induced secretion of the immunosuppressive cytokine IL‐10, and upregulated the expression of CD137 (4‐1BB) and CD25. Overall, our data indicate that oxygen tension is a key regulator of CD8⁺ T‐cell function and fate and suggest that IL‐10 release may be an unanticipated component of CD8⁺ T cell‐mediated immune responses in most in vivo microenvironments.     

IL‐7 is superior to IL‐2 for ex vivo expansion of tumour‐specific CD4+ T cells

It is well established that tumours hinder both natural and vaccine‐induced tumour‐specific CD4⁺ T‐cell responses. Adoptive T‐cell therapy has the potential to circumvent functional tolerance and enhance anti‐tumour protective responses. While protocols suitable for the expansion of cytotoxic CD8⁺ T cells are currently available, data on tumour‐specific CD4⁺ T cells remain scarce. We report here that CD4⁺ T cells sensitized to tumour‐associated Ag in vivo, proliferate in vitro in response to IL‐7 without the need for exogenous Ag stimulation and accumulate several folds while preserving a memory‐like phenotype. Both cell proliferation and survival accounts for the outgrowth of tumour‐sensitized T cells among other memory and naive lymphocytes following exposure to IL‐7. Also IL‐2, previously used to expand anti‐tumour CTL, promotes tumour‐specific CD4⁺ T‐cell accumulation. However, IL‐7 is superior to IL‐2 at preserving lymphocyte viability, in vitro and in vivo, maintaining those properties, that are required by helper CD4⁺ T cells to confer therapeutic efficacy upon transplantation in tumour‐bearing hosts. Together our data support a unique role for IL‐7 in retrieving memory‐like CD4⁺ T cells suitable for adoptive T‐cell therapy.     

Circulating CD137+CD8+ T cells accumulate along with increased functional regulatory T cells and thoracic tumour burden in lung cancer patients

CD137 is a promising target for immunostimulation strategies against cancer. Previous studies showed that CD137⁺CD8⁺ T cells are enriched in antitumour effector T cells in both preclinical tumour models and cancer patients, but to date, such T cells in the blood of lung cancer patients have not been sufficiently investigated. In this study, circulating antigen‐activated CD8⁺ T cell subsets, identified as CD137⁺CD8⁺ or PD‐1⁺ (programmed cell death protein 1) CD8⁺, and regulatory T cells (Treg), identified as CD4⁺CD25⁺CD127^low/?, in 40 untreated lung cancer patients and in 49 age‐ and sex‐matched healthy controls (HCs) were assessed by flow cytometry. Results were evaluated for associations with lung cancer patient clinical characteristics. Correlations between antigen‐activated CD8⁺ T cells and effector Treg (CTLA‐4⁺ [cytotoxic T‐lymphocyte antigen 4] CD4⁺CD25⁺CD127^low/?) were also investigated. Higher percentages of PD‐1⁺, CD137⁺ and PD‐1⁺CD137⁺ amongst CD8⁺ T cells were observed in lung cancer patients compared with HCs. The percentages of CD137⁺CD8⁺ and PD‐1⁺CD137⁺CD8⁺ T cell subsets amongst CD8⁺ T cells were positively correlated with thoracic tumour burden and were strongly positively correlated with the percentage of effector Treg subset. Smoking patients harboured higher percentages of the PD‐1⁺CD8⁺ T cell subset compared with non‐smoking patients. This study demonstrated that circulating antigen‐activated CD8⁺ T cells accumulated in lung cancer patients along with increased effector Treg and thoracic tumour burden. These findings aid a better understanding of immune‐host interactions in lung cancer patients using peripheral blood, and further support immunotherapeutic intervention strategies using combination therapy for differential control of Treg and activation of tumour‐specific effector T cells.     

IL‐15 is critical for the maintenance and innate functions of self‐specific CD8+ T cells

IL‐15 is a pleiotropic cytokine involved in host defense as well as autoimmunity. IL‐15‐deficient mice show a decrease of memory phenotype (MP) CD8⁺ T cells, which develop naturally in naïve mice and whose origin is unclear. It has been shown that self‐specific CD8⁺ T cells developed in male H‐Y antigen‐specific TCR transgenic mice share many similarities with naturally occurring MP CD8⁺ T cells in normal mice. In this study, we found that H‐Y antigen‐specific CD8⁺ T cells in male but not female mice decreased when they were crossed with IL‐15‐deficient mice, mainly due to impaired peripheral maintenance. The self‐specific TCR transgenic CD8⁺ T cells developed in IL‐15‐deficient mice showed altered surface phenotypes and reduced effector functions ex vivo. Bystander activation of the self‐specific CD8⁺ T cells was induced in vivo during infection with Listeria monocytogenes, in which proliferation but not IFN‐γ production was IL‐15‐dependent. These results indicated important roles for IL‐15 in the maintenance and functions of self‐specific CD8⁺ T cells, which may be included in the naturally occurring MP CD8⁺ T‐cell population in naïve normal mice and participate in innate host defense responses.     

HBV‐specific CD4+ cytotoxic T cells in hepatocellular carcinoma are less cytolytic toward tumor cells and suppress CD8+ T cell‐mediated antitumor immunity

In East Asia and sub‐Saharan Africa, chronic infection is the main cause of the development of hepatocellular carcinoma, an aggressive cancer with low survival rate. Cytotoxic T cell‐based immunotherapy is a promising treatment strategy. Here, we investigated the possibility of using HBV‐specific CD4⁺ cytotoxic T cells to eliminate tumor cells. The naturally occurring HBV‐specific cytotoxic CD4⁺ and CD8⁺ T cells were identified by HBV peptide pool stimulation. We found that in HBV‐induced hepatocellular carcinoma patients, the HBV‐specific cytotoxic CD4⁺ T cells and cytotoxic CD8⁺ T cells were present at similar numbers. But compared to the CD8⁺ cytotoxic T cells, the CD4⁺ cytotoxic T cells secreted less cytolytic factors granzyme A (GzmA) and granzyme B (GzmB), and were less effective at eliminating tumor cells. In addition, despite being able to secrete cytolytic factors, CD4⁺ T cells suppressed the cytotoxicity mediated by CD8⁺ T cells, even when CD4⁺CD25⁺ regulator T cells were absent. Interestingly, we found that interleukin 10 (IL‐10)‐secreting Tr1 cells were enriched in the cytotoxic CD4⁺ T cells. Neutralization of IL‐10 abrogated the suppression of CD8⁺ T cells by CD4⁺CD25^? T cells. Neither the frequency nor the absolute number of HBV‐specific CD4⁺ cytotoxic T cells were correlated with the clinical outcome of advanced stage hepatocellular carcinoma patients. Together, this study demonstrated that in HBV‐related hepatocellular carcinoma, CD4⁺ T cell‐mediated cytotoxicity was present naturally in the host and had the potential to exert antitumor immunity, but its capacity was limited and was associated with immunoregulatory properties.     

IL‐15‐dependent CD8+CD122+ T cells ameliorate experimental autoimmune encephalomyelitis by modulating IL‐17 production by CD4+ T cells

Interleukin‐15 (IL‐15) is an inflammatory cytokine whose role in autoimmune diseases has not been fully elucidated. Th17 cells have been shown to play critical roles in experimental autoimmune encephalomyelitis (EAE) models. In this study, we demonstrate that blockade of IL‐15 signaling by TMβ‐1 mAb treatment aggravated EAE severity. The key mechanism was not NK‐cell depletion but depletion of CD8⁺CD122⁺ T cells. Adoptive transfer of exogenous CD8⁺CD122⁺ T cells to TMβ‐1‐treated mice rescued animals from severe disease. Moreover, transfer of preactivated CD8⁺CD122⁺ T cells prevented EAE development and significantly reduced IL‐17 secretion. Naïve effector CD4⁺CD25^? T cells cultured with either CD8⁺CD122⁺ T cells from wild‐type mice or IL‐15 transgenic mice displayed lower frequencies of IL‐17A production with lower amounts of IL‐17 in the supernatants when compared with production by effector CD4⁺CD25^? T cells cultured alone. Addition of a neutralizing antibody to IL‐10 led to recovery of IL‐17A production in Th17 cultures. Furthermore, coculture of CD8⁺CD122⁺ T cells with effector CD4⁺ T cells inhibited their proliferation significantly, suggesting a regulatory function for IL‐15 dependent CD8⁺CD122⁺ T cells. Taken together, these observations suggest that IL‐15, acting through CD8⁺CD122⁺ T cells, has a negative regulatory role in reducing IL‐17 production and Th17‐mediated EAE inflammation.     

Increasing inflationary T‐cell responses following transient depletion of MCMV‐specific memory T cells

Murine CMV (MCMV) infection induces effector CD8⁺ T cells that continue to increase in frequency after acute infection (“inflation”) and are stably maintained at a high frequency, with up to 20% of the CD8⁺ T‐cell compartment being specific for one epitope, although the flexibility and turnover of these populations is not fully defined. Here we report that effector/memory CD8⁺ T cells induced by MCMV can be paradoxically boosted following transient depletion of epitope specific CD8⁺ T cells. Treatment of MCMV‐infected mice with MHC‐Class I‐saporin tetramers led to partial (80–90%) depletion of epitope‐specific CD8⁺ T cells—rapidly followed by a rebound, leading to expansion and maintenance of up to 40% of total CD8⁺ T cells, with minimal changes in response to a control epitope (M45). These data indicate the tight balance between host and virus during persistent infection and the functional flexibility of the “inflated” CD8⁺ T cell responses during persistent infection.     

Mycobacterium tuberculosis‐specific CD8+ T cells are functionally and phenotypically different between latent infection and active disease

Protective immunity to Mycobacterium tuberculosis (Mtb) remains poorly understood and the role of Mtb‐specific CD8⁺ T cells is controversial. Here we performed a broad phenotypic and functional characterization of Mtb‐specific CD8⁺ T cells in 326 subjects with latent Mtb infection (LTBI) or active TB disease (TB). Mtb‐specific CD8⁺ T cells were detected in most (60%) TB patients and few (15%) LTBI subjects but were of similar magnitude. Mtb‐specific CD8⁺ T cells in LTBI subjects were mostly T_EMRA cells (CD45RA⁺CCR7^?), coexpressing 2B4 and CD160, and in TB patients were mostly T_EM cells (CD45RA^?CCR7^?), expressing 2B4 but lacking PD‐1 and CD160. The cytokine profile was not significantly different in both groups. Furthermore, Mtb‐specific CD8⁺ T cells expressed low levels of perforin and granulysin but contained granzymes A and B. However, in vitro‐expanded Mtb‐specific CD8⁺ T cells expressed perforin and granulysin. Finally, Mtb‐specific CD8⁺ T‐cell responses were less frequently detected in extrapulmonary TB compared with pulmonary TB patients. Mtb‐specific CD8⁺ T‐cell proliferation was also greater in patients with extrapulmonary compared with pulmonary TB. Thus, the activity of Mtb infection and clinical presentation are associated with distinct profiles of Mtb‐specific CD8⁺ T‐cell responses. These results provide new insights in the interaction between Mtb and the host immune response.     

Polyfunctional response by ImmTAC (IMCgp100) redirected CD8+ and CD4+ T cells

The success of immune system‐based cancer therapies depends on a broad immune response engaging a range of effector cells and mechanisms. Immune mobilizing monoclonal T cell receptors (TCRs) against cancer (ImmTAC™ molecules: fusion proteins consisting of a soluble, affinity enhanced TCR and an anti‐CD3 scFv antibody) were previously shown to redirect CD8⁺ and CD4⁺ T cells against tumours. Here we present evidence that IMCgp100 (ImmTAC recognizing a peptide derived from the melanoma‐specific protein, gp100, presented by HLA‐A*0201) efficiently redirects and activates effector and memory cells from both CD8⁺ and CD4⁺ repertoires. Using isolated subpopulations of T cells, we find that both terminally differentiated and effector memory CD8⁺ T cells redirected by IMCgp100 are potent killers of melanoma cells. Furthermore, CD4⁺ effector memory T cells elicit potent cytotoxic activity leading to melanoma cell killing upon redirection by IMCgp100. The majority of T cell subsets belonging to both the CD8⁺ and CD4⁺ repertoires secrete key pro‐inflammatory cytokines (tumour necrosis factor‐α, interferon‐γ, interleukin‐6) and chemokines (macrophage inflammatory protein‐1α‐β, interferon‐γ‐inducible protein‐10, monocyte chemoattractant protein‐1). At an individual cell level, IMCgp100‐redirected T cells display a polyfunctional phenotype, which is a hallmark of a potent anti‐cancer response. This study demonstrates that IMCgp100 induces broad immune responses that extend beyond the induction of CD8⁺ T cell‐mediated cytotoxicity. These findings are of particular importance because IMCgp100 is currently undergoing clinical trials as a single agent or in combination with check point inhibitors for patients with malignant melanoma.     

Co‐inhibitory profile and cytotoxicity of CD57+PD‐1– T cells in end‐stage renal disease patients

Blockade of the CD80/86‐CD28 pathway by belatacept after kidney transplantation is associated with an increased risk of rejection compared with standard, calcineurin inhibitor (CNI)‐based therapy. CD28^– T cells, which express CD57, are not susceptible to belatacept treatment. High numbers of CD4⁺CD57⁺programmed death 1 (PD‐1)^– T cells pretransplantation have been associated with a higher chance of rejection, although conflicting data have been reported. To investigate the working mechanism behind this possible higher chance of rejection, we studied the expression of co‐inhibitory molecules (CD223, CD244 and PD‐1), proliferative capacity and cytotoxic potential of fluorescence activated cell sorted (FACS) CD4⁺CD57⁺PD‐1^– and CD8⁺CD57⁺PD‐1^– T cells, and their CD57^– control populations, after alloantigen stimulation. The effect of belatacept on the cytotoxic capacity of pretransplantation peripheral blood mononuclear cells from 20 patients who received belatacept post‐transplantation was also tested. Expression of co‐inhibitory molecule CD223 increased by approximately 10‐fold after allogeneic stimulation in all four T cell subsets. Proliferation and up‐regulation of CD244 and PD‐1 was observed for CD4⁺CD57^‐PD‐1^– T cells after allogeneic stimulation, but no up‐regulation of these markers occurred on CD8⁺ T cells or CD4⁺CD57⁺PD‐1^– T cells. However, CD4⁺CD57⁺PD‐1^– T cells and, to a lesser extent, CD8⁺CD57⁺PD‐1^– T cells displayed higher cytotoxicity as indicated by granzyme B expression. Belatacept inhibited the cytotoxic potential of CD4⁺CD57⁺PD‐1^– T cells (median of inhibition 31%, P < 0·01) and CD8⁺CD57⁺PD‐1^– T cells (median of inhibition 10%, P < 0·05). In conclusion, alloantigen‐activated CD4⁺CD57⁺PD‐1^– T cells exhibited a less proliferative but more cytotoxic profile than their CD57^– counterparts. Their cytotoxic capacity can be inhibited partly by belatacept and was not associated with development of rejection after kidney transplantation.     

Programmed death (PD)‐1 molecule and its ligand PD‐L1 distribution among memory CD4 and CD8 T cell subsets in human immunodeficiency virus‐1‐infected individuals

Human immunodeficiency virus (HIV)‐1 causes T cell anergy and affects T cell maturation. Various mechanisms are responsible for impaired anti‐HIV‐1‐specific responses: programmed death (PD)‐1 molecule and its ligand PD‐L1 are negative regulators of T cell activity and their expression is increased during HIV‐1 infection. This study examines correlations between T cell maturation, expression of PD‐1 and PD‐L1, and the effects of their blockade. Peripheral blood mononuclear cells (PBMC) from 24 HIV‐1⁺ and 17 uninfected individuals were phenotyped for PD‐1 and PD‐L1 expression on CD4⁺ and CD8⁺ T cell subsets. The effect of PD‐1 and PD‐L1 blockade on proliferation and interferon (IFN)‐γ production was tested on eight HIV‐1⁺ patients. Naive (CCR7⁺CD45RA⁺) CD8⁺ T cells were reduced in HIV‐1 aviraemic (P = 0·0065) and viraemic patients (P = 0·0130); CD8 T effector memory subsets [CCR7^‐CD45RA^–(T_EM)] were increased in HIV‐1⁺ aviraemic (P = 0·0122) and viraemic (P = 0·0023) individuals versus controls. PD‐1 expression was increased in CD4 naive (P = 0·0496), central memory [CCR7⁺CD45RA^– (T_CM); P = 0·0116], T_EM (P = 0·0037) and CD8 naive T cells (P = 0·0133) of aviraemic HIV‐1⁺versus controls. PD‐L1 was increased in CD4 T_EMRA (CCR7^‐CD45RA⁺, P = 0·0119), CD8 T_EM (P = 0·0494) and CD8 T_EMRA (P = 0·0282) of aviraemic HIV‐1⁺versus controls. PD‐1 blockade increased HIV‐1‐specific proliferative responses in one of eight patients, whereas PD‐L1 blockade restored responses in four of eight patients, but did not increase IFN‐γ‐production. Alteration of T cell subsets, accompanied by increased PD‐1 and PD‐L1 expression in HIV‐1 infection contributes to anergy and impaired anti‐HIV‐1‐specific responses which are not rescued when PD‐1 is blocked, in contrast to when PD‐L1 is blocked, due possibly to an ability to bind to receptors other than PD‐1.     

Cytomegalovirus vector expressing RAE‐1γ induces enhanced anti‐tumor capacity of murine CD8+ T cells

Designing CD8⁺ T‐cell vaccines, which would provide protection against tumors is still considered a great challenge in immunotherapy. Here we show the robust potential of cytomegalovirus (CMV) vector expressing the NKG2D ligand RAE‐1γ as CD8⁺ T cell‐based vaccine against malignant tumors. Immunization with the CMV vector expressing RAE‐1γ, delayed tumor growth or even provided complete protection against tumor challenge in both prophylactic and therapeutic settings. Moreover, a potent tumor control in mice vaccinated with this vector can be further enhanced by blocking the immune checkpoints TIGIT and PD‐1. CMV vector expressing RAE‐1γ potentiated expansion of KLRG1⁺ CD8⁺ T cells with enhanced effector properties. This vaccination was even more efficient in neonatal mice, resulting in the expansion and long‐term maintenance of epitope‐specific CD8⁺ T cells conferring robust resistance against tumor challenge. Our data show that immunomodulation of CD8⁺ T‐cell responses promoted by herpesvirus expressing a ligand for NKG2D receptor can provide a powerful platform for the prevention and treatment of CD8⁺ T‐cell sensitive tumors.     

Altered effector functions of virus‐specific and virus cross‐reactive CD8+ T cells in mice immunized with related flaviviruses

Memory cross‐reactive CD8⁺ T‐cell responses may induce protection or immunopathology upon secondary viral challenge. To elucidate the potential role of T cells in sequential flavivirus infection, we characterized cross‐reactive CD4⁺ and CD8⁺ T‐cell responses between attenuated and pathogenic Japanese encephalitis virus (JEV) and pathogenic West Nile virus (WNV). A previously reported WNV NS4b CD8⁺ T‐cell epitope and its JEV variant elicited CD8⁺ T‐cell responses in both JEV‐ and WNV‐infected mice. The peptide variant homologous to the immunizing virus induced greater cytokine secretion and activated higher frequencies of epitope‐specific CD8⁺ T cells. However, there was a virus‐dependent, peptide variant‐independent pattern of cytokine secretion; the IFNγ⁺‐to‐IFNγ⁺TNFα⁺ CD8⁺ T‐cell ratio was greater in JEV‐ than in WNV‐infected mice. Despite similarities in viral burden for pathogenic WNV and JEV viruses, CD8⁺ T cells from pathogenic JEV‐immunized mice exhibited functional and phenotypic profiles similar to those seen for the attenuated JEV strain. Patterns of killer cell lectin‐like receptor G1 (KLRG1) and CD127 expression differed by virus type, with a rapid expansion and contraction of short‐lived effector cells in JEV infection and persistence of high levels of short‐lived effector cells in WNV infection. Such cross‐reactive T‐cell responses to primary infection may affect the outcomes of sequential flavivirus infections.     

Depletion of tumor‐induced Treg prior to reconstitution rescues enhanced priming of tumor‐specific,therapeutic effector T cells in lymphopenic hosts

We reported previously that vaccination of reconstituted, lymphopenic mice resulted in a higher frequency of tumor‐specific effector T cells with therapeutic activity than vaccination of normal mice. Here, we show that lymphopenic mice reconstituted with spleen cells from tumor‐bearing mice (TBM), a situation that resembles the clinical condition, failed to generate tumor‐specific T cells with therapeutic efficacy. However, depletion of CD25⁺ Treg from the spleen cells of TBM restored tumor‐specific priming and therapeutic efficacy. Adding back TBM CD25⁺ Treg to CD25^? naïve and TBM donor T cells prior to reconstitution confirmed their suppressive role. CD25⁺ Treg from TBM prevented priming of tumor‐specific T cells since subsequent depletion of CD4⁺ T cells did not restore therapeutic efficacy. This effect may not be antigen‐specific as three histologically distinct tumors generated CD25⁺ Treg that could suppress the T‐cell immune response to a melanoma vaccine. Importantly, since ex vivo depletion of CD25⁺ Treg from TBM spleen cells prior to reconstitution and vaccination fully restored the generation of therapeutic effector T cells, even in animals with established tumor burden, we have initiated a translational clinical trial of this strategy in patients with metastatic melanoma.     

Adoptive transfer of cytomegalovirus‐specific effector CD4+ T cells provides antiviral protection from murine CMV infection

Cytomegalovirus (CMV) infects a majority of the human population and establishes a life‐long persistence. CMV infection is usually asymptomatic but the virus carries pathogenic potential and causes severe disease in immunocompromised individuals. T‐cell‐mediated immunity plays an essential role in control of CMV infection and adoptive transfer of CMV‐specific CD8⁺ T cells restores viral immunity in immunosuppressed patients but a role for CD4⁺ T cells remains elusive. Here, we analyzed in adoptive transfer studies the features and antiviral functions of virus‐specific CD4⁺ T cells during primary murine CMV (MCMV) infection. MCMV‐specific CD4⁺ T cells expanded upon MCMV infection and displayed an effector phenotype and function. Adoptive transfer of in vivo activated MCMV‐specific CD4⁺ T cells to immune‐compromised mice was protective during pathogenic MCMV infection and IFN‐γ was a crucial mediator of this protective capacity. Moreover, co‐transfer of low doses of both MCMV‐specific CD4⁺ T cells and CD8⁺ T cells synergized in control of lytic viral replication in immune‐compromised mice. Our data reveal a pivotal antiviral role for virus‐specific CD4⁺ T cells in protection from pathogenic CMV infection and provide evidence for their antiviral therapeutic potential.     

CD122+CD8+ Treg suppress vaccine‐induced antitumor immune responses in lymphodepleted mice

Lymphodeleption prior to adoptive transfer of tumor‐specific T cells greatly improves the clinical efficacy of adoptive T‐cell therapy for patients with advanced melanoma, and increases the therapeutic efficacy of cancer vaccines in animal models. Lymphodepletion reduces competition between lymphocytes, and thus creates “space” for enhanced expansion and survival of tumor‐specific T cells. Within the lymphodepleted host, Ag‐specific T cells still need to compete with other lymphocytes that undergo lymphopenia‐driven proliferation. Herein, we describe the relative capacity of naïve T cells, Treg, and NK cells to undergo lymphopenia‐driven proliferation. We found that the major population that underwent lymphopenia‐driven proliferation was the CD122⁺ memory‐like T‐cell population (CD122⁺CD8⁺ Treg), and these cells competed with Ag‐driven proliferation of melanoma‐specific T cells. Removal of CD122⁺CD8⁺ Treg resulted in a greater expansion of tumor‐specific T cells and tumor infiltration of functional effector/memory T cells. Our results demonstrate the lymphopenia‐driven proliferation of CD122⁺CD8⁺ Treg in reconstituted lymphodepleted mice limited the antitumor efficacy of DC vaccination in conjunction with adoptive transfer of tumor‐specific T cells.     

Phenotypic analysis of perennial airborne allergen‐specific CD4+ T cells in atopic and non‐atopic individuals

Background Accumulating evidence suggests that T cells play an important role in the pathogenesis of atopic dermatitis (AD); yet, little is known of the differentiation status of CD4⁺ T cells specific for common environmental allergens, such as the major cat allergen, Fel d 1. Objective To determine the frequency, differentiation phenotype and function of circulating Fel d 1‐specific CD4⁺ T cells in adult individuals with severe persistent AD in comparison with healthy controls. Methods Using HLA class II tetrameric complexes based on a HLA‐DPB1^*0401‐restricted Fel d 1 epitope, ex vivo and cultured T cell frequency and phenotype were analysed in individuals with AD and healthy controls. Cytokine secretion was measured by ex vivo and cultured IL‐4 and IFN‐γ ELISpots. Results Ex vivo Fel d 1‐specific DPB1^*0401‐restricted CD4⁺ T cells in both atopics and non‐atopics express high levels of CCR7, CD62L, CD27 and CD28, placing the cells largely within the central memory subgroup. However, the functional phenotype was distinct, with greater IL‐4 production from the cells derived from atopics, which correlated with disease severity. Conclusions and Clinical Relevance Circulating Fel d 1‐specific DPB1^*0401‐restricted CD4⁺ T cells in both atopic and non‐atopic donors maintain a central memory phenotype; however in atopics, the cells had greater Th2 effector function, compatible with a disease model of altered antigen delivery in atopic individuals. Cite this as: L. R. Crack, H. W. Chan, T. McPherson and G. S. Ogg, Clinical & Experimental Allergy, 2011 (41) 1555–1567.